Approximately 15 million Americans have obstructive sleep apnea (OSA). Portions of the respiratory tract collapse in OSA patients resulting in the blockage of the airways and reduced blood oxygen levels. As blood oxygen levels drop, the patient awakens and gasps for air. This cycle is repeated many times during the night. Left untreated, OSA is associated with a significant increased risk of cardiovascular events including hypertension, stroke and heart attack. Obstructive sleep apnea has been associated with a high risk for motor vehicle accidents, and is thought to account for 15-20% of the 40-50,000 deaths and almost 4,000,000 emergency department visits annually. Continuous Positive Air Pressure, or CPAP, is an effective and widely recognized therapy for obstructive sleep apnea but is often under prescribed by physicians and under-utilized by patients. The positive air pressure prevents the airways of the respiratory tract from collapsing, preventing the apneic event.
The basic mechanism of a CPAP device is based on creating a positive pressure gradient between the device and the patient. As a result, when the mask is open to atmosphere, a constant jet will be generated from the pressure gradient between the device and the atmosphere. When the mask is placed around the patient's face, the jet is stopped and a positive pressure builds between the CPAP and the lungs of the patient. This positive pressure maintains the airways from collapsing. If the mask is not sealed correctly, the air will then follow the path of least resistance, thus escaping out into the atmosphere where the pressure is lower. The patient will experience this as air bleeding out from the system, but more importantly, the positive pressure that is the basic of operation for CPAP cannot be maintained. A tight fluid seal is required to maintain a positive air pressure throughout the entire upper airway. If the fluid seal is broken, continuous positive pressure is lost and the patient's upper airways are at risk of collapsing. To prevent this pressure loss, a tight seal in the form of a mask must be placed over the mouth and nose.
An alternative to a full face mask is a nasal apparatus that only works if the patient does not open his or her mouth at night. If the patient opens his or her mouth, the fully pressurized respiratory tract will lose pressurization as the air will follow the path of least resistance and rush out of the mouth. For patients that open their mouths, an additional apparatus to keep the mouth closed must be employed. Chin straps and bite guards are two approaches to help mouth breathers keep their mouths closed during sleep.
CPAP is efficacious, but is not well tolerated by patients. Studies show that somewhere between 46% and 83% of patients are not compliant with CPAP therapy and remove the CPAP device early in the night or skip use altogether. Compliance is poor due to the discomfort and inconvenience associated with CPAP. Issues that result in patient non-compliance include mask discomfort, nasal dryness, congestion, difficulty adapting to the unrelenting positive air pressure across the mouth and nose, abdominal bloating due to air entering the digestive tract, and facial skin irritation due to the requirement of a tight seal between the mask and face.
Accordingly, a need exists for alternative treatments for obstructive sleep apnea.